1. Field of the Invention
This invention has relation to floating structures capable of unloading bulk materials from ship to cargo barges or lighters, for loading bulk materials from lighters to ships, for loading such materials from lighters to shore, from shore to lighters, and to and from shore and ships.
2. Description of the Prior Art
It is advantageous to be able to rapidly load ships with bulk materials such as grain and grain byproducts at locations where dock facilities for receiving deep draft vessels are not available. This has been accomplished in the past by loading the bulk material onto cargo barges or lighters, anchoring the ship against substantial movement in waters of safe depth, and then providing some kind of an unloader to transfer the bulk material from the lighters to the hold of the ship. Often the ship will be anchored "midstream" at the point where a river runs into a gulf, bay, or larger body of water.
The time during which the ship is necessarily at anchor represents a very substantial economic investment or drain on the shipper. It is highly advantageous to do everything possible to reduce the time for loading or unloading the ship and thus reducing what is called the "turn-around time".
In order to accomplish this purpose in the past, a tower mounted on a single barge has been equipped with a horizontal boom extending transversely outwardly from the tower and the barge to have position over lighters at one side and over a ship at the other. A clam shell-type grab bucket running on a bucket trolley along this boom has been used to transport the bulk material from the lighter to the ship for onloading and from the ship to the lighter for offloading. An early patent showing such a structure is U.S. Pat. No. 734,974 to Shoosmith, patented in July of 1903. In order to try to keep the boom from rocking with the rocking of the barge as the bucket trolley, bucket and material move along the boom, Shoosmith moved a large counterweight transversely along the bottom of the barge in opposition to the direction of movement of the grab bucket along the boom.
More recently, others have attempted to obtain stability for such a structure by moving a counterweight along the boom in direction opposite to the movement of the bucket and bucket trolley and the bulk material in the bucket trolley. See, for example, the following patents:
______________________________________ U.S. Pat. No. Inventor Issued ______________________________________ 4,220,246 Ray 9/1980 1,343,630 Locarni 6/1920 ______________________________________
This method of moving a counterweight in opposition to movement of a bucket, bucket trolley and load carried in the bucket has also been used extensively where the tower is mounted on land. Such structures are useful where docking facilities are such that a ship can come right up against the side of the pier. See the following patents.
______________________________________ U.S. Pat. No. Inventor Issued ______________________________________ 4,067,446 Ray 1/1978 3,642,148 Durand 2/1972 3,722,705 Gould 3/1973 4,113,112 Ray 9/1978 654,739 Lancaster 7/1900 4,039,086 Ray 8/1977 ______________________________________
It has been suggested to stabilize a vertical tower and horizontal boom structure mounted on a single barge or pontoon by providing fixed weights at one or both ends of the boom. See the following patents:
______________________________________ U.S. Pat. No. Inventor Issued ______________________________________ 4,074,817 Ray 2/1978 4,074,818 Ray 2/1978 ______________________________________
This same technique has been suggested for use with a vertical tower and horizontal boom mounted on the ground. See U.S. Pat. No. 3,752,326, granted to Levingston in August of 1973.
The difficulty with these "single barge" or "single fixed tower" structures is that the counterweight effect can only be approximate. For example, when the grab bucket initially fills and closes and picks up the weight of the bulk material, the boom suffers a severe imbalance, first when the weight of the bucket is removed from the boom when the bucket is dropped, jaws opened, into the ship hold or lighter preparatory to picking up its bulk material load, and second, when the bucket jaws are closed and the entire weight of the bucket and the bulk materials inside are suddenly applied to the boom. This inevitably results in some deflection of the boom, and some vertical swinging of the boom until the forces are absorbed. This will cause the bucket to swing in a vertical plane. To minimize this effect, the digging and dumping operations must be slowed down substantially to avoid the possibility of severe damage caused by and to the swinging bucket.
Also, in the case of single barge or pontoon structure, this instability is added to by the effect of any swell and/or wave action.
Further, the use of counterweights and counterbalances means that the overall structure must be designed to carry this extra, otherwise nonproductive, counterbalancing weight. In the structures where the counterbalance actually moves at the same time as the bucket trolley, bucket and bulk material load in the bucket, the acceleration and deceleration of the counterweight are unwelcome energy losses.
It has been found that very substantial increases in the stability of a bulk material unloader cam be obtained by utilizing two spaced-apart parallel pontoons fixedly positioned one with respect to the other by overhead bolsters. See the following U.S. patents:
______________________________________ U.S. Pat. No. Inventor Issued ______________________________________ 3,938,676 Croese 2/1976 3,673,974 Harper 7/1972 3,894,503 McClure 7/1975 4,106,637 Marsden 8/1978 ______________________________________
The Croese patent discloses an onloader having two pontoons spread wide enough apart so that a single cargo barge or lighter can be positioned therebetween. To attempt to gain further stability against rocking, the bulk material is removed from the lighter through the instrumentality of an endless bucket conveyor elevator 13, and further endless conveyor legs which are counterbalanced to deliver the grain to the hold of a ship. Apparently no provision is made for offloading from the ship to the lighter. Further, the disclosure contemplates that all or a substantial portion of the hatch covers on the lighter must be removed from the lighter before the endless bucket conveyor can start removing bulk materials therefrom. Also, when a particular lighter has been emptied, the flow of bulk material from the floating unloading installation to the ship must stop until the hatch covers are placed back on top of the lighter, and the lighter is hauled away and another loaded lighter takes its place, and until sufficient hatch covers are removed from the loaded lighter to let the conveying mechanism again start to operate.
The problem of maintaining stability between the lighters and the bulk material unloader and between the unloader and a ship are clearly illustrated in the solution to the problem disclosed in the patent to Marsden. As seen in that patent, the bulk material unloader or floating transfer vessel is moored to the side of a ship, and the bulk material is literally blown or aimed in a stream into the ship through downspouts located high above it. In this way, the importance of movement between the ship and the unloader is minimized. However, this is at the expense of creating large amounts of dust in unloading materials such, for example, as grain and grain byproducts.
In Marsden, the transfer vessel or bulk unloader is of such a nature that its hull can be partially filled with water, a lighter pulled into the interior of the transfer vessel, and then the water pumped out to "strand" the lighter on the floor of the bulk unloader or vessel. Thus there will be no relative movement whatever between the lighter and the unloader, and a plurality of endless bucket diggers can be used to move along the floor of the lighter with precision to scoop up grain and move it to an elevating means where it can be fed into the ship through downspouts as aforementioned.
This operation is obviously not a continuous one inasmuch as water must be allowed into the unloader or transfer vessel to partially submerge it, one lighter must be towed inside of the unloader, the hatch covers all removed, water pumped back out of the vessel to have the vessel pick up the weight of and firmly support the lighter, all before the grain or other bulk material removal process can be begun. When removal has been completed, the hatch covers must be replaced, and water let back into the unloader vessel to allow the lighter to float free so that it can be replaced with yet another lighter, and then the entire cycle completed. Obviously the "down time" is extensive.
The patents to Harper and McClure make use of twin pontoons for supporting revolving cranes. However, these twin pontoons are not designed so that cargo lighters can be brought between them. Instead, the structures of the patents are designed to support the revolving cranes for other purposes such, for example, as servicing offshore oil rigs. Further, each of the twin pontoon structures are designed to be semi-submersible in order to try to avoid the action of heavy seas and the effect of such action on the stability of the structures.
As suggested above, an ability to move cargo lighter hatch covers off of the hatches of the lighters and to replace them without interrupting the action of a bulk material unloader in constantly moving bulk materials to ships from lighters or to lighters from ships is very important. Typically, before the present invention, in fair weather, each lighter was moved to position adjacent an auxiliary platform such, for example, as that shown in the Harper and McClure patents, and a revolving crane was used to lift the hatch covers off of the lighter hatches one at a time and to stack them on such platform. Then after the lighter was fully loaded or unloaded by a prior art unloader, depending on whether it was in an offloading or an onloading situation, the lighter would again be towed to the auxiliary vessel where the covers are positioned back on the hatches, one after the other.
This would be fairly efficient timewise if there were always enough uncovered lighters available to the bulk unloader or other apparatus so that the lighter could be exchanged without waiting for the lighter hatch covers to be removed. However, when handling bulk materials which are moisture sensitive, when the rains began, all of the lighters which were uncovered, including the lighter currently being loaded or unloaded, had to be towed to the vicinity of the revolving crane, all of the covers put back on, and the operation of loading or unloading shut down until the weather cleared.
Efforts have been made to overcome this problem. See the following patents:
______________________________________ U.S. Pat. No. Inventor Issued ______________________________________ 3,938,676 Croese 2/1976 4,106,637 Marsden 8/1978 3,283,923 Schynder 11/1966 4,238,036 Lamer et al 12/1980 3,774,787 Ledinsky 11/1973 ______________________________________
As previously pointed out, in the disclosure of the Croese patent, many if not all of the lighter hatch covers must be removed before the unloading can begin. In case of rain, the Croese lighter will be virtually unprotected except perhaps for a small portion of the end opposite the digging apparatus, so digging will have to stop and the covers will have to be returned.
The patent to Marsden shows a lighter hatch cover 20 which, it is said, is supported above the lighter by "overhead block and tackle 22 and are held aloft and out of the way." Because the automated digging and conveying apparatus moves the entire length of the lighter, it is necessary that beginning of this digging operation be delayed until all of the hatch covers are off and up out of the way. Once the automated digging and cleanup have occurred, it will be necessary that all of the hatch covers be replaced before the lighter can be removed from the transfer vessel or bulk unloader and replaced with another loaded and covered lighter. There is no provision in the teaching of Marsden for offloading of the ship and consequent loading of the lighters situated in the transfer vessel or bulk unloader.
The Lamer et al patent presents a heavy, elaborate and expensive apparatus for replacing hatch covers on ship's cargo hold openings. The hatch cover crane of Lamer lifts the hatches, tilts them up on one end and moves them so that the other end is in alignment with the hatch and then lowers the hatch cover into place. It is not believed to be particularly pertinent to the present invention, but does illustrate the difficulty and importance of properly handling hatch covers.
The patent to Schnyder shows a traveling crane mounted on tracks along a building and extending above the roof top of the building. The crane travels along over the top of the building to remove roof sections and stack them one on top of the other at one of the ends of the building. Obviously the structure of Schnyder does not have to be concerned with alignment of the roof sections inasmuch as the rails which carry the crane are permanently fastened with respect to the roof. Thus Schnyder is not helpful in facing the problem of rapid realignment of lighter hatch covers on hatches, which was the problem solved, for example, by the aforementioned patent to Lamer et al.
Because no problem of alignment is involved, it is believed that the patent to Ledinsky is not particularly pertinent to the present invention.
Before the present invention, where it was deemed essential that the machine operator be able to see precisely the location of a bucket mounted from a bucket trolley on a horizontal boom, for example, the operator's control cab was often either made a part of the bucket trolley structure or was fitted to ride along the boom with the bucket trolley. The alternative was to permanently affix the operator's cab to the central tower, and to transmit visual, audible and/or electronic signals to the operator when the bucket, for example, reached a location where he could no longer properly observe it. See the following patents:
______________________________________ U.S. Pat. No. Inventor Issued ______________________________________ 3,402,824 Zweifel 9/1968 3,722,705 Gould 3/1973 4,067,446 Ray 1/1978 4,074,817 Ray 2/1978 4,074,818 Ray 2/1978 ______________________________________
Experience has shown that a man riding in a control cab mounted on a trolley or to ride with a trolley is subject to intense vibrations, often causing back problems and absenteeism resulting in severe physical difficulties for the operator and lost time and Workman's Compensating claims made against the owner.
Having the cab situated at a fixed location where the operator cannot see properly and/or is instructed by signals received from persons who can view the operation results either in a slowdown of operations to decrease the chance of accidents or in an increase of accidents due to poor visibility for the operator and lack of coordination with the signaller(s).
What was needed before the present invention was a bulk material unloader which can operate in "midstream" in adjacent relation to a ship and can operate continuously and without interruption from the time operations begin to fill or empty a particular hold of a ship until such time as that operation is completed, and without any interruption of the normal operation due to the movement and handling of the cargo lighters involved.
Also needed was a bulk material unloader which can be easily converted from onloading operation from lighters to unloader to ship to offloading operation from ship to unloader to lighters.
A search was made of an earlier form of the invention set out herein. Applicants and those in privity with them are aware of no prior art which is closer than that discussed above and are aware of no prior art which anticipates the claims made herein.